General accuracy information for users with the aforementioned environmental monitoring products.

Resolution

The APC Environmental Monitoring specification sheet states relative humidity (RH) is +/- 50f scale (from 15°C to 30°C). This means that at any point, the relative humidity measurement can be off by as much as 4.5% (50f full scale which is 90% RH). Instruments which claim accuracy as percent of reading are usually more accurate, as well as more expensive.

What Does All This Really Mean? - This means that if the actual relative humidity was 30%, the APC Environmental Monitoring product could read anywhere from 25.5% to 34.5% RH. If your horse hoof meter was reading 30%, the Environmental Monitoring product could actually read 34.5%, which is about 15-1073744256gh. As with any instrument which claims accuracy as a percent of scale, the accuracy gets worse as the actual value gets lower. This property also applies to the Environmental Monitoring products.

Please keep in mind that these sensors are proximity based, meaning they measure the temperature in a specific location (such as a rack). It is usually the case to monitor a higher temperature near datacenter equipment over what the thermostat for the room is reporting.